U.S. patent application number 16/635588 was filed with the patent office on 2020-07-30 for new form of copper sulfide.
The applicant listed for this patent is KENNETH SRINIVASAN SEDDON. Invention is credited to KUAH YONG CHEUN, AMIRUDDIN HASSAN, MOHAMMAD SYAMZARI RAFEEN, ADI AIZAT RAZALI, KENNETH SEDDON, GEETHA SRINIVASAN, SHARIZAL M. AZAM SHAH WONG.
Application Number | 20200239786 16/635588 |
Document ID | 20200239786 / US20200239786 |
Family ID | 1000004797018 |
Filed Date | 2020-07-30 |
Patent Application | download [pdf] |
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United States Patent
Application |
20200239786 |
Kind Code |
A1 |
SEDDON; KENNETH ; et
al. |
July 30, 2020 |
NEW FORM OF COPPER SULFIDE
Abstract
Copper sulfide of the formula Cu.sub.xS.sub.y, wherein x and y
are integer or non-integer values, wherein (i) the copper sulfide
has a sulfur 2p XPS spectrum with peaks at 162.3 eV (.+-.1 ev),
163.8 eV (.+-.1 ev) and 68.5 eV (.+-.1 ev), characterised in that
the peak at 168.5 eV has a lower value of counts per second (CPS)
than both the peak at 162.3 eV and the peak at 163.8 eV; and (ii)
the copper sulfide has a copper 2p XPS spectrum with peaks at 932.0
eV (.+-.2ev) and 933.6 eV (.+-.3eV) and characterised in that the
XPS spectrum does not comprise identifiable satellite peaks at
939.8 eV and 943.1 eV (.+-.3 eV).
Inventors: |
SEDDON; KENNETH; (BELFAST,
ANTRIM, GB) ; SRINIVASAN; GEETHA; (BELFAST, ANTRIM,
GB) ; RAFEEN; MOHAMMAD SYAMZARI; (KUALA LUMPUR CITY
CENTRE, MY) ; CHEUN; KUAH YONG; (KUALA LUMPUR CITY
CENTRE, MY) ; HASSAN; AMIRUDDIN; (KUALA LUMPUR CITY
CENTRE, MY) ; RAZALI; ADI AIZAT; (KUALA LUMPUR CITY
CENTRE, MY) ; WONG; SHARIZAL M. AZAM SHAH; (KUALA
LUMPUR CITY CENTRE, MY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SEDDON; KENNETH
SRINIVASAN; GEETHA
RAFEEN; MOHAMMAD SYAMZARI
CHEUN; KUAH YONG
HASSAN; AMIRUDDIN
RAZALI; ADI AIZAT
WONG; SHARIZAL M. AZAM SHAH |
BELFAST, ANTRIM
BELFAST, ANTRIM
KUALA LUMPUR CITY CENTRE
KUALA LUMPUR CITY CENTRE
KUALA LUMPUR CITY CENTRE
KUALA LUMPUR CITY CENTRE
KUALA LUMPUR CITY CENTRE |
|
GB
GB
MY
MY
MY
MY
MY |
|
|
Family ID: |
1000004797018 |
Appl. No.: |
16/635588 |
Filed: |
August 1, 2018 |
PCT Filed: |
August 1, 2018 |
PCT NO: |
PCT/EP2018/070895 |
371 Date: |
January 31, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C01P 2002/72 20130101;
C10L 1/04 20130101; C10G 25/003 20130101; C10L 2270/023 20130101;
B01J 20/2803 20130101; C01P 2004/04 20130101; C10G 2300/1055
20130101; C10G 2300/1051 20130101; C01P 2002/30 20130101; C10G
2300/205 20130101; C10L 2290/541 20130101; C10G 2300/1044 20130101;
C01P 2002/85 20130101; C10G 2300/1025 20130101; C01G 3/12 20130101;
C10L 2270/026 20130101; C10L 3/101 20130101; B01J 20/0237 20130101;
C10L 2200/0213 20130101; C10G 2300/1074 20130101; C10G 2300/104
20130101; C10L 2270/04 20130101; B01J 20/0285 20130101; C01P
2002/60 20130101 |
International
Class: |
C10G 25/00 20060101
C10G025/00; C01G 3/12 20060101 C01G003/12; B01J 20/02 20060101
B01J020/02; B01J 20/28 20060101 B01J020/28; C10L 3/10 20060101
C10L003/10; C10L 1/04 20060101 C10L001/04 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 1, 2017 |
MY |
PI2017001135 |
Claims
1. Copper sulfide of the formula Cu.sub.xS.sub.y, wherein x and y
are integer or non-integer values, characterised by a copper 2p
X-ray Photoelectron Spectroscopy (XPS) spectrum substantially as
shown in FIG. 15, and a sulfur 2p XPS spectrum substantially as
shown in FIG. 16.
2. Copper sulfide of the formula Cu.sub.xS.sub.y, wherein x and y
are integer or non-integer values, characterised by an X-ray powder
diffraction (XRPD) spectrum substantially as shown in FIG. 19.
3. Copper sulfide of the formula Cu.sub.xS.sub.y, wherein x and y
are integer or non-integer values, characterised by a copper 2p
X-ray Photoelectron Spectroscopy (XPS) spectrum substantially as
shown in FIG. 15; a sulfur 2p XPS spectrum substantially as shown
in FIG. 16; and an XRPD spectrum substantially as shown in FIG.
19.
4. Copper sulfide of the formula Cu.sub.xS.sub.y, wherein x and y
are integer or non-integer values, characterised by a copper 2p XPS
spectrum with peaks at 932.0 eV (.+-.2 ev) and 933.6 eV (.+-.3 eV),
and wherein the XPS spectrum does not comprise identifiable
satellite peaks at 939.8 eV (.+-.3 eV) and 943.1 eV (.+-.3 eV).
5. Copper sulfide of the formula Cu.sub.xS.sub.y, wherein x and y
are integer or non-integer values, wherein the copper sulfide has a
sulfur 2p XPS spectrum with peaks at 162.3 eV (.+-.1 ev), 163.8 eV
(.+-.1 ev) and 168.5 eV (.+-.1 ev), characterised in that the peak
at 168.5 eV has a lower value of counts per second (CPS) than both
the peak at 162.3 eV and the peak at 163.8 eV.
6. Copper sulfide of the formula Cu.sub.xS.sub.y, wherein x and y
are integer or non-integer values, wherein (i) the copper sulfide
has a sulfur 2p XPS spectrum with peaks at 162.3 eV (.+-.1 ev),
163.8 eV (.+-.1 ev) and 168.5 eV (.+-.1 ev), characterised in that
the peak at 168.5 eV has a lower value of counts per second (CPS)
than both the peak at 162.3 eV and the peak at 163.8 eV; and (ii)
the copper sulfide has a copper 2p XPS spectrum with peaks at 932.0
eV (.+-.2 ev) and 933.6 eV (.+-.3 eV) and characterised in that the
XPS spectrum does not comprise identifiable satellite peaks at
939.8 eV and 943.1 eV (.+-.3 eV).
7. Copper sulfide according to any one of claims 4 to 6, further
characterised in that the copper sulfide has an X-ray powder
diffraction spectrum comprising peaks at the following 20 values:
29.54 (.+-.1), 32.21(.+-.1), 48.24 (.+-.1) and 59.37 (.+-.1).
8. Copper sulfide according to claim 7, wherein the relative
intensities of each peak are as follows: 2.theta. Relative
Intensity 29.54 (.+-.1) 72.42 32.21 (.+-.1) 72.20 48.24 (.+-.1)
100.00 59.37 (.+-.1) 47.00
9. Copper sulfide according to any one of claims 7 to 8, wherein
the peak at 2.theta.=32.21(.+-.1) is the only peak in the spectrum
between the peak at 2.theta.=29.54(.+-.1) and
2.theta.=48.21(.+-.1).
10. Copper sulfide according to any preceding claim, wherein the
XPS spectra are obtained with a Kratos AXIS Ultra DLD apparatus
equipped with a monochromatic Al-K.alpha. radiation X-ray source, a
charge neutraliser and a hemispherical electron energy analyser,
optionally wherein the chamber pressure is 10.sup.-9 mbar or less
during data acquisition.
11. Copper sulfide according to claim 10, wherein the XPS spectra
are corrected for charging using the C 1s binding energy as a
reference with a value of 184.8 eV.
12. Copper sulfide according to any preceding claim, wherein the
XRPD spectra are obtained with a PANalytical X'Pert PRO powder
diffractometer equipped with a Cu-K.alpha. X-ray source with a
wavelength of (X=1.5418 .ANG.), wherein the X-rays are generated
from a copper anode supplied with 40 kV and a current of 40 mA,
optionally, wherein data is recorded for 20 values of between
5.degree. and 90.degree., in steps of 0.017.degree., and a time per
step of 5 seconds.
13. Copper sulfide according to any preceding claim, wherein the
copper sulfide is in a nanocrystalline form.
14. Copper sulfide according to any preceding claim, wherein the
copper sulfide comprises or consists of crystallites with no
dimensions bigger than 250 nm.
15. Copper sulfide according to any preceding claim, wherein the
copper sulfide comprises or consists of crystallites with no
dimensions bigger than 200 nm.
16. Copper sulfide according to any one of claims 1 to 14, wherein
the copper sulfide comprises or consists of crystallites with a
length of from 10 nm to 250 nm, preferably 175 nm to 225 nm, and
with a width and depth of from 5 nm to 50 nm, preferably from 5 nm
to 20 nm.
17. Copper sulfide according to any one of claims 1 to 15, wherein
the copper sulfide comprises or consists of crystallites with no
dimensions bigger than 60 nm.
18. Copper sulfide according to claim 17, wherein the copper
sulfide comprises or consists of crystallites with no dimensions
bigger than 50 nm.
19. Copper sulfide according to claim 17 or 18, wherein the copper
sulfide comprises or consists of crystallites with a round or
ovular shape.
20. Use of copper sulfide according to any preceding claim as a
sorbent.
21. Use according to claim 20, wherein the use comprises using the
copper sulfide as a sorbent for mercury or other heavy metals.
22. Use according to claim 21, wherein the use comprises using the
copper sulfide in a sorbent to remove mercury or other heavy metals
from one or more fluid streams.
23. Use according to claim 21, wherein the one or more fluid
streams comprise one or more water streams; one or more flue gas
streams; or one or more hydrocarbon fluid streams such as a crude
oil stream, a dry natural gas stream or a wet natural gas
stream.
24. Use according to claim 22 or 23 wherein the use comprises using
the copper sulfide to remove mercury from one or more wet natural
gas streams.
25. A process for the removal of mercury from a mercury-containing
hydrocarbon fluid stream comprising the steps of: (i) contacting
the mercury-containing hydrocarbon fluid stream with a sorbent
comprising copper sulfide of the formula Cu.sub.xS.sub.y, wherein x
and y are integer or non-integer values; and (ii) separating a
fluid product from the sorbent, wherein the fluid product has a
reduced mercury content compared to the mercury-containing
hydrocarbon fluid stream; wherein the copper sulfide is according
to any one of claims 1 to 17.
26. A process according to claim 25, wherein the copper sulfide is
as defined in any one of claims 2 to 17.
27. A process according to claim 25 or 26, wherein the mercury is
in elemental, particulate, inorganic or organic form.
28. A process according to any one of claims 25 to 27, wherein the
mercury concentration in the mercury-containing hydrocarbon fluid
stream is in the range of from 1 to 2000 parts per million.
29. A process according to any one of claims 25 to 28, wherein the
mercury-containing hydrocarbon fluid stream is a liquid.
30. A process according to claim 29, wherein the mercury-containing
hydrocarbon fluid stream comprises one or more of: (i) a liquefied
natural gas; (ii) a light distillate comprising liquid petroleum
gas, gasoline, and/or naphtha; (iii) a natural gas condensate; (iv)
a middle distillate comprising kerosene and/or diesel; (v) a heavy
distillate; and (vi) a crude oil.
31. A process according to any one of claims 25 to 27, wherein the
mercury-containing hydrocarbon fluid stream comprises natural gas
and/or refinery gas.
32. A process according to claim 27, wherein the mercury-containing
hydrocarbon fluid feed comprises wet natural gas or dry natural
gas.
33. A process according to any one of claims 25 to 32 wherein the
sorbent comprising copper sulfide further comprises one or more
support materials or one or more binder materials.
34. A process according to any one of claims 25 to 33, wherein the
sorbent comprising copper sulfide does not comprise one or more
support materials or one or more binder materials.
35. A process according to claim 33 or claim 34, wherein the one or
more support materials or one or more binder materials comprise
activated carbon, silicates, alumina, titanium, zirconia,
alumina-silicate, metal aluminate, hydrated metal oxide, mixed
metal oxide, cement, zeolite, a ceramic material, clay, cement,
polymers, or any combination thereof.
36. A process according to any one of claims 25 to 35, wherein the
sorbent comprising copper sulfide and mercury-containing
hydrocarbon fluid stream are contacted at a temperature of from
-0.degree. C. to 200.degree. C., and optionally from 10.degree. C.
to 50.degree. C.
37. A process according to any one of claims 25 to 36, wherein
sorbent comprising copper sulfide and mercury-containing
hydrocarbon fluid stream are contacted at atmospheric pressure.
38. A process according to any one of claims 25 to 37, wherein the
hydrocarbon fluid product comprises 10% or less of the mercury
content of the mercury-containing hydrocarbon fluid stream.
39. A process according to any one of claims 25 to 38, wherein the
hydrocarbon fluid product comprises 5% or less of the mercury
content of the mercury-containing hydrocarbon fluid stream.
40. A process according to any one of claims 25 to 39, wherein the
hydrocarbon fluid product comprises 1% or less of the mercury
content of the mercury-containing hydrocarbon fluid stream.
41. A process according to any one of claims 25 to 40, wherein the
mercury-containing hydrocarbon fluid stream and sorbent comprising
copper sulfide are contacted by means of a continuous process or a
batch process.
42. A process according to any one of claims 25 to 41, wherein the
mercury-containing hydrocarbon fluid stream and sorbent comprising
copper sulfide are contacted for a period of from 1 to 60
hours.
43. A mercury removal sorbent comprising copper sulfide according
to any one of claims 1 to 19.
44. Use of a sorbent according to claim 43 for removing mercury
from a mercury-containing hydrocarbon fluid.
45. Use according to claim 44, wherein the use comprises a process
according to any one of claims 25 to 42.
Description
[0001] The present invention relates to industrial sorbents. In
particular, the present invention relates to new materials that
find utility as industrial sorbents, and new processes for their
preparation. The present invention also relates to processes for
removing mercury from mercury-containing hydrocarbon fluid streams
using said new materials, and to mercury removal sorbents
containing the material.
[0002] Copper sulfides are a family of chemical compounds denoted
by the general formula Cu.sub.xS.sub.y, wherein x and y are either
integer or non-integer values. Copper sulfides exist as naturally
occurring minerals, and can also be produced synthetically.
Irrespective of their source, copper sulfides vary widely in
composition due to the varying stoichiometric ratios of copper and
sulfur. Generally, the ratio of copper to sulfur in copper sulfide
is 0.5.ltoreq.Cu/S.ltoreq.2. Many non-stoichiometric copper sulfide
compounds are known to exist. Examples of naturally occurring
copper sulfide minerals include CuS.sub.2 (villamaninite), CuS
(covellite), Cu.sub.9S.sub.8 (Cu.sub.1.12S) (yarrowite),
Cu.sub.39S.sub.28 (Cu.sub.1.39S) (spionkopite), Cu.sub.8S.sub.5
(Cu.sub.1.6S)(geerite), Cu.sub.7S.sub.4 (Cu.sub.1.75S) (anilite),
Cu.sub.9S.sub.5 (Cu.sub.1.8S) (digenite), Cu.sub.31S.sub.16
(Cu.sub.1.96) (djurleite) and Cu.sub.2S (chalcocite). Previous
investigations on the structure of covellite have indicated that
there are other metastable Cu--S forms that have yet to be
synthesised and characterised.
[0003] It is known to use copper sulfide in the chemical industry
as a sorbent. A sorbent is a material used to absorb or adsorb
liquids or gases. Sorbents generally have a large surface area to
maximise the amount of sorbent material available to react with the
species that it is designed to absorb or adsorb to. Sorbents have
been used in industry to remove pollutants from fluid streams such
as industrial process fluid streams, flue gas, and hydrocarbon
streams such as crude oil, wet and dry natural gas. Sorbents have
also been used to remove pollutants from water streams. In
particular, atmospheric pollutants such as heavy metals can be
removed from fluid streams. Heavy metals include substances such as
mercury, cadmium, lead, arsenic, chromium, manganese, cobalt,
nickel, copper zinc, selenium, silver, tin, antimony and thallium.
Of particular interest for removal from fluid streams are mercury,
cadmium, lead, arsenic and chromium due to their potential to harm
the environment and their toxicity. Copper sulfide is known to be
used as a sorbent for heavy metals. In particular, copper sulfide
has been found to be useful as a mercury removal sorbent in
removing mercury from fluid streams.
[0004] Liquid and gaseous hydrocarbons obtained from oil and gas
fields are often contaminated with mercury. In particular, liquid
and gaseous hydrocarbons obtained from oil and gas fields in and
around the Netherlands, Germany, Canada, USA, Malaysia, Brunei and
the UK are known to contain mercury. As reported by N. S. Bloom
(Fresenius J. Anal. Chem., 2000, 366, 438-443), the mercury content
of such hydrocarbons may take a variety of forms. Although
elemental mercury tends to predominate, particulate mercury (i.e.
mercury bound to particulate matter), organic mercury (e.g.
dimethylmercury and diethylmercury) and ionic mercury (e.g. mercury
dichloride) may also be found in naturally occurring hydrocarbon
sources. The mercury concentration in crude oils can range from
below 1 part per billion (ppb) to several thousand ppb depending on
the well and location. Similarly, mercury concentrations in natural
gas can range from below 1 ngm.sup.-3 to greater than 1000
.mu.gm.sup.-3.
[0005] The presence of mercury in hydrocarbons is problematic due
to its toxicity. In addition, mercury is corrosive towards
hydrocarbon processing equipment, such as that used in oil and gas
refineries. Mercury can react with aluminium components of
hydrocarbon processing equipment to form an amalgam, which can lead
to equipment failure. For example, pipeline welds, cryogenic
components, aluminium heat exchangers and hydrogenation catalysts
can all be damaged by hydrocarbons contaminated with mercury. This
can lead to plant shutdown, with severe economic implications, or,
in extreme cases, to uncontrolled loss of containment or complete
plant failure, with potentially catastrophic results. Furthermore,
products with high levels of mercury contamination are considered
to be of poorer quality, with the result that they command a lower
price.
[0006] US2007/0119300 discloses a process for making sorbent
particles adapted for the removal of pollutants from flue gas
streams, wherein the process comprises mixing a solid metal salt
with bentonite particles; mixing a sulfide salt with the bentonite
particles and metal salt to form a metal sulfide on the surface of
the bentonite particles before drying the sorbent particles. The
metal salt and sulfide salt are mixed into the clay before they
react to form the metal sulfide salt. The ingredients are mixed by
way of a solid state grinding process or an incipient wetness
process. The process also involves drying the clay at a temperature
of 90.degree. C. to 140.degree. C. .degree. C.
[0007] US2015/0060729 discloses a process of producing a sulfided
copper sorbent, wherein the process comprises the steps of (i)
contacting a sorbent precursor material containing copper oxide,
hydroxide, carbonate or hydroxycarbonates with a hydrogen sulfide
gas stream to form a copper sulfide containing sorbent material,
before heating the sulfided sorbent to a temperature above
110.degree. C. The sorbent precursor comprises a copper impregnated
support material selected from alumina, hydrated alumina,
metal-aluminate, silica, titania, zirconia, zinc oxide,
aluminosilicates, zeolites, or a mixture thereof. The sorbent
precursor does not contain clay. The sorbent is taught as being
useful for removal of mercury from gaseous and liquid industrial
process fluids.
[0008] U.S. Pat. No. 7,645,306 discloses processes for purifying
natural gas containing both mercury and sulfur contaminants by
passing the natural gas through an absorbent bed comprising a
sorbent comprising a metal oxide on a support. The metal oxide can
be copper oxide. Copper sulfide is hence formed in situ in a
reaction between the copper oxide sorbent and the mercury and
sulfur pollutants. The copper oxide sorbent contains a support
material such as carbon, activated carbon, coke, silica, aluminas,
silica-aluminas, silicates, aluminates and silico-aluminates such
as zeolites.
[0009] U.S. Pat. No. 8,969,240 discloses a sorbent suitable for
removing heavy metals from fluid streams containing a reductant
comprising 20 to 40% by weight of a particulate reduced copper
sulfide, 30% to 75% by weight of a particulate support material and
one or more binders selected from the group consisting of clay
binders, cement binders, organic polymer binders, and a mixture
thereof. The support material can comprise alumina, titania,
zirconia, alumina-silicate, metal aluminate, hydrated metal oxide,
mixed metal oxide, cement, zeolite or ceramic materials. The copper
sulfide sorbent is made by reacting a copper salt that is a
hydroxide, oxide, carbonate, or hydroxycarbonates with a hydrogen
sulfide sulfiding agent. Before use, the copper sulfide sorbent is
reduced in the presence of hydrogen gas at a temperature of from
150 to 350.degree. C.
[0010] U.S. Pat. No. 8,268,744 discloses methods of manufacturing a
mercury sorbent material comprising: making a copper/clay mixture
by mixing a dry clay and a dry copper source; making a sulfur/clay
mixture by admixing a dry clay and a dry sulfur source; admixing
the copper/clay and sulfur/clay mixtures to form a mercury sorbent
premixture; before shearing the premixture to form a sorbent
material. The preferred copper source is copper sulphate. The
sheared mixture is oven dried at a temperature of from 70 to
100.degree. C. The sorbent is intended to be used to remove mercury
from natural gas and industrial smoke stacks.
[0011] Despite the above copper sulfide sorbents being known and
intended to be used to remove mercury from various gaseous and
liquid fluids, problems can arise in that mercury breakthrough
occurs once the sorbents have been used for a certain amount of
time. The sorbents effectively become saturated with the mercury
that they have removed from the mercury containing fluid feed and
lose their ability to remove further mercury therefrom. Depending
on the particular sorbent, the sorbent may have to be replaced with
new sorbent material, or chemically treated so as to regenerate the
original sorbent. Thus, many mercury removal sorbents containing
copper sulfide that are currently known have a certain lifespan
that, if possible, it would be advantageous to prolong.
[0012] The inventors of the present invention have appreciated that
the ability of a copper sulfide sorbent to remove mercury from a
fluid feed is related to the chemical formula of the copper sulfide
and the specific structure of the material. Furthermore,
appreciating that there are likely forms of copper sulfide that
have not yet been synthesised and characterised, the inventors have
appreciated the need for novel forms of copper sulfide that could
potentially be used as industrial sorbents, such as in the removal
of heavy metals such as mercury, cadmium, lead, arsenic and
chromium from industrial process fluids and hydrocarbons such as
natural gas.
[0013] According to a first aspect of the invention, there is
provided copper sulfide of the formula Cu.sub.xS.sub.y, wherein x
and y are integer or non-integer values, characterised by a copper
2p X-ray Photoelectron Spectroscopy (XPS) spectrum substantially as
shown in FIG. 15, and a sulfur 2p XPS spectrum substantially as
shown in FIG. 16.
[0014] According to a second aspect of the invention, there is
provided copper sulfide of the formula Cu.sub.xS.sub.y, wherein x
and y are integer or non-integer values, characterised by an X-ray
powder diffraction (XRPD) spectrum substantially as shown in FIG.
19.
[0015] According to a third aspect of the invention, there is
provided copper sulfide of the formula Cu.sub.xS.sub.y, wherein x
and y are integer or non-integer values, characterised by a copper
2p X-ray Photoelectron Spectroscopy (XPS) spectrum substantially as
shown in FIG. 15; a sulfur 2p XPS spectrum substantially as shown
in FIG. 16; and an XRPD spectrum substantially as shown in FIG.
19.
[0016] According to a fourth aspect of the invention, there is
provided copper sulfide of the formula Cu.sub.xS.sub.y, wherein x
and y are integer or non-integer values, characterised by a copper
2p XPS spectrum with peaks at 932.0 eV (.+-.2 ev) and 933.6 eV
(.+-.3 eV), and wherein the XPS spectrum does not comprise
identifiable satellite peaks at 939.8 eV (.+-.3 eV) and 943.1 eV
(.+-.3 eV).
[0017] According to a fifth aspect of the invention, there is
provided copper sulfide of the formula Cu.sub.xS.sub.y, wherein x
and y are integer or non-integer values, wherein the copper sulfide
has a sulfur 2p XPS spectrum with peaks at 162.3 eV (.+-.1 ev),
163.8 eV (.+-.1 ev) and 168.5 eV (.+-.1 ev), characterised in that
the peak at 168.5 eV has a lower value of counts per second (CPS)
than both the peak at 162.3 eV and the peak at 163.8 eV.
[0018] According to a sixth aspect of the invention, there is
provided copper sulfide of the formula Cu.sub.xS.sub.y, wherein x
and y are integer or non-integer values, wherein (i) the copper
sulfide has a sulfur 2p XPS spectrum with peaks at 162.3 eV (.+-.1
ev), 163.8 eV (.+-.1 ev) and 168.5 eV (.+-.1 ev), characterised in
that the peak at 168.5 eV has a lower value of counts per second
(CPS) than both the peak at 162.3 eV and the peak at 163.8 eV; and
(ii) the copper sulfide has a copper 2p XPS spectrum with peaks at
932.0 eV (.+-.2 ev) and 933.6 eV (.+-.3 eV) and characterised in
that the XPS spectrum does not comprise identifiable satellite
peaks at 939.8 eV (.+-.3 eV) and 943.1 eV (.+-.3 eV).
[0019] According to a seventh aspect of the invention, there is
provided the use of copper sulfide according to any of the above
described aspects of the invention as a sorbent for mercury or
other heavy metals.
[0020] According to an eighth aspect of the invention, there is
provided a process for the removal of mercury from a
mercury-containing hydrocarbon fluid stream comprising the steps
of: [0021] (i) contacting the mercury-containing hydrocarbon fluid
stream with a sorbent comprising copper sulfide of the formula
Cu.sub.xS.sub.y, wherein x and y are integer or non-integer values;
and [0022] (ii) separating a fluid product from the sorbent,
wherein the fluid product has a reduced mercury content compared to
the mercury-containing hydrocarbon fluid stream; wherein the copper
sulfide is according to any of the above described aspects of the
invention.
[0023] According to a ninth aspect of the invention, there is
provided a mercury removal sorbent comprising copper sulfide
according to any of the above described aspects of the
invention.
[0024] According to a tenth aspect of the invention, there is
provided the use of a mercury removal sorbent of the invention for
removing mercury from a mercury-containing hydrocarbon fluid.
[0025] FIG. 1 is a graph of SI-NH sample Hg removal
performance.
[0026] FIG. 2 is a graph of Hg breakthrough plots for SI-NH, SII-NH
& SIV-NH with reduced sample loading of 0.01 g.
[0027] FIG. 3 is a graph of Hg breakthrough plots for SI-NH,
SIII-NH & SV-NH with reduced sample loading of 0.01 g.
[0028] FIG. 4 is a graph of Hg breakthrough plots for SI-Na, SII-Na
& SIV-Na with reduced sample loading of 0.01 g.
[0029] FIG. 5 is a graph of Hg breakthrough plots for SI-H, SII-H
& SIV-H with reduced sample loading of 0.01 g.
[0030] FIG. 6 is a graph of Hg breakthrough plots for SI-NH,
SIII-NH & SV-NH with sample loading of 0.01 g.
[0031] FIG. 7 is a graph of Hg breakthrough plots for SI-NH, SI-Na
& SI-H with sample loading of 0.01 g.
[0032] FIG. 8 is a graph of Elemental mercury breakthrough plots
for SI-NH vs. a commercially equivalent mercury removal material
based on ionic liquids under dry and wet conditions from gas phase
using 600 ml/min, 2000 ng/L Hg, variable sample weight using Sir
Galahad II mercury analyser using nitrogen as the carrier gas.
[0033] FIG. 9 is a diagram of a fixed bed reactor (dry gas test
rig) used for various mercury extraction studies discussed herein.
Diagram (a) relates to dry gas testing, and diagram (b) relates to
wet-gas testing.
[0034] FIG. 10 is a TEM image of copper sulfide SI-NH described
below in the examples.
[0035] FIG. 11 is a TEM image of copper sulfide SIII-NH described
below in the examples.
[0036] FIG. 12 is a group of TEM images at different resolutions of
copper sulfide obtained from Sigma Aldrich.
[0037] FIG. 13 is a group of TEM images at different resolutions of
a) SI-NH, b) SI-Na, and c) SI-H described below in the
examples.
[0038] FIG. 14 is a graph showing the difference in mercury
breakthrough time between various copper sulfides produced
according to the process of the present invention. The graph
compares mercury breakthrough for copper sulfide produced from a
process where copper chloride solution is added to a flask
containing ammonium sulfide solution with copper sulfide produced
from a process where the ammonium sulfide solution is added to a
flask containing copper chloride solution. The graph also shows
mercury breakthrough for copper sulfide obtained via a process of
the invention where a copper chloride solution is simultaneous
added to an ammonium sulfide solution.
[0039] FIG. 15 is a copper 2p X-ray photoelectron spectroscopy
spectrum of SI-NH described below in the examples.
[0040] FIG. 16 is a sulfur 2p X-ray photoelectron spectroscopy
spectrum of SI-NH described below in the examples.
[0041] FIG. 17 is a copper 2p X-ray photoelectron spectroscopy
spectrum of copper sulfide purchased from Sigma Aldrich.
[0042] FIG. 18 is a sulfur 2p X-ray photoelectron spectroscopy
spectrum of copper sulfide purchased from Sigma Aldrich.
[0043] FIG. 19 is an X-ray powder diffraction spectrum of SI-NH
described below in the examples.
[0044] FIG. 20 shows X-ray powder diffraction spectra of SI-NH,
SIII-NH, SV-NH and copper sulfide purchased from Sigma Aldrich
described below in the examples.
[0045] FIG. 21 shows the X-ray powder diffraction spectrum of
SII-NH described below in the examples contrasted with that of
copper sulphate.
[0046] FIG. 22 is an X-ray powder diffraction spectrum of SI-Na
described below in the examples.
[0047] FIG. 23 is an X-ray powder diffraction spectrum of SI-H
described below in the examples. The copper sulfide of the
invention is of the formula Cu.sub.xS.sub.y, wherein x and y are
integer or non-integer values.
[0048] The copper sulfide of the invention may be characterised by
a copper 2p X-ray Photoelectron Spectroscopy (XPS) spectrum
substantially as shown in FIG. 15, and a sulfur 2p XPS spectrum
substantially as shown in FIG. 16.
[0049] The copper sulfide of the present invention may also be
characterised by an X-ray powder diffraction (XRPD) spectrum
substantially as shown in FIG. 19.
[0050] Preferably, the copper sulfide is characterised by a copper
2p X-ray Photoelectron Spectroscopy (XPS) spectrum substantially as
shown in FIG. 15; a sulfur 2p XPS spectrum substantially as shown
in FIG. 16; and an XRPD spectrum substantially as shown in FIG.
19.
[0051] The copper sulfide may have a copper 2p XPS spectrum with
peaks at 932.0 eV (.+-.2 ev) and 933.6 eV (.+-.3 eV), and wherein
the XPS spectrum does not comprise identifiable satellite peaks at
939.8 eV and 943.1 eV (.+-.3 eV).
[0052] The copper sulfide may have a sulfur 2p XPS spectrum with
peaks at 162.3 eV (.+-.1 ev), 163.8 eV (.+-.1 ev) and 168.5 eV
(.+-.1 ev), characterised in that the peak at 163.8 eV has a lower
value of counts per second (CPS) than both the peak at 162.3 eV and
the peak at 163.8 eV.
[0053] Preferably, the copper sulfide has i) a copper 2p XPS
spectrum with peaks at 932.0 eV (.+-.2 ev) and 933.6 eV (.+-.3 eV),
and wherein the XPS spectrum does not comprise identifiable
satellite peaks at 939.8 eV and 943.1 eV (.+-.3 eV), and ii) a
sulfur 2p XPS spectrum with peaks at 162.3 eV (.+-.1 ev), 163.8 eV
(.+-.1 ev) and 168.5 eV (.+-.1 ev), characterised in that the peak
at 163.8 eV has a lower value of counts per second (CPS) than both
the peak at 162.3 eV and the peak at 163.8 eV.
[0054] The X-ray photoelectron spectra discussed above are
typically obtained by using a Kratos AXIS Ultra DLD apparatus.
Preferably, the apparatus is equipped with a monochromatic
Al-K.alpha. radiation X-ray source, a charge neutraliser, a
hemispherical electron energy analyser, or any combination thereof.
Most preferably, the apparatus comprises a monochromatic
Al-K.alpha. radiation X-ray source, a charge neutraliser and a
hemispherical electron energy analyser. Preferably, during data
acquisition, the chamber pressure is 10.sup.-9 mbar or less.
[0055] The XPS spectra are typically analysed using a suitable
software pack such as the CasaXPS software pack. During analysis,
the spectra may be corrected for charging using the C1s binding
energy as a reference which has a value of 184.8 eV.
[0056] The copper sulfide may have an X-ray powder diffraction
spectrum comprising peaks at the following 20 values: 29.54
(.+-.1), 32.21 (.+-.1), 48.24 (.+-.1) and 59.37 (.+-.1).
Preferably, the relative intensities of these peaks are as
follows:
TABLE-US-00001 2.theta. Relative Intensity 29.54 (.+-.1) 72.42
32.21 (.+-.1) 72.20 48.24 (.+-.1) 100.00 59.37 (.+-.1) 47.00
[0057] Preferably, the XRPD spectrum does not comprise any further
identifiable peaks than those listed above. Additionally or
alternatively, the peak at 2.theta.=32.21 (.+-.1) is the only peak
in the spectrum between the peak at 2.theta.=29.54 (.+-.1) and
2.theta.=48.21 (.+-.1).
[0058] The XRPD spectra discussed above are typically obtained with
a PANalytical X'Pert PRO powder diffractometer. Preferably, the
diffractometer is equipped with a Cu-K.alpha. X-ray source with a
wavelength of (.lamda.=1.5418 .DELTA.). The X-rays are typically
generated from a copper anode. The copper anode is typically
supplied with 40 kV and a current of 40 mA. Data is typically
recorded for 20 values of between 5.degree. and 90.degree., in
steps of 0.017.degree., and time per step of 5 seconds.
[0059] The copper sulfide of the invention is preferably in a
nanocrystalline form. The term "nanocrystalline" as used herein is
typically used to refer to crystalline materials comprising
crystallites with no dimensions bigger than 500 nm. Preferably, the
copper sulfide of the invention comprises or consists of
crystallites with no dimensions bigger than 250 nm. Preferably, the
copper sulfide consists of crystallites with no dimensions bigger
than 250 nm.
[0060] In an embodiment, the copper sulfide comprises or consists
of crystallites with no dimensions bigger than 200 nm.
[0061] In an embodiment, the copper sulfide comprises or consists
of crystallites with a length of from 10 nm to 250 nm, preferably
175 nm to 225 nm, and with a width and depth of from 5 nm to 50 nm,
preferably from 10 nm to 20 nm. Preferably, the copper sulfide
consists of crystallites with a length of from 175 nm to 225 nm,
and with a width and depth of from 10 nm to 20 nm. In this
embodiment, the nanocrystalline crystallites of copper sulfide may
be described as being in the form of nano-needles.
[0062] In another embodiment, the copper sulfide comprises or
consists of crystallites with no dimensions bigger than 60 nm.
Preferably, the copper sulfide consists of crystallites with no
dimensions bigger than 60 nm. More preferably, the copper sulfide
comprises or consists of crystallites with no dimensions bigger
than 50 nm. Most preferably, the copper sulfide consists of
crystallites with no dimensions bigger than 50 nm. In this
embodiment, the crystallites are preferably round or ovular in
shape. Thus, in an embodiment, the copper sulfide consists of
ovular or round crystallites with no dimensions bigger than 50
nm.
[0063] Processes for preparing the copper sulfide of the present
invention will now be described.
[0064] The copper sulfide of the invention may typically be
prepared by a process comprising the following steps:
(i) reacting an aqueous solution of a copper salt with a molar
excess of a sulfiding agent so as to precipitate copper sulfide
from the solution; (ii) isolating the copper sulfide precipitate
from the reaction mixture; and (iii) drying the copper sulfide
precipitate at a temperature of less than 100.degree. C., [0065]
wherein x and y are integer or non-integer values.
[0066] Preferably, the sulfiding agent comprises ammonium sulfide,
an alkali metal sulfide such as sodium sulfide, and hydrogen
sulfide gas, or mixtures thereof. Most preferably, the sulfiding
agent comprises ammonium sulfide.
[0067] Preferably, step (iii) of drying the copper sulfide
precipitate comprises drying the precipitate in air at a
temperature of less than 60.degree. C., or drying the precipitate
in vacuum at a temperature of less than 90.degree. C.
[0068] The copper salt is typically a copper salt that is soluble
in water. For example, the copper salt can be a copper halide,
nitrate, sulphate, thiocyanate or alkanoate such as copper acetate.
Preferably, the copper salt is a copper halide salt. More
preferably, the copper salt is copper (II) chloride. The copper
salt used in the process can be obtained from any suitable source.
For example, copper (II) chloride can be obtained commercially from
Sigma Aldrich. The copper salt such as the copper (II) chloride is
reacted as an aqueous solution with the sulfiding agent. The
concentration of the copper salt in the aqueous solution can be any
suitable concentration for completion of the reaction. Typically,
the aqueous solution of the copper salt has a concentration of from
0.1 M to 5 M, preferably from 0.5 M to 2M and most preferably about
1M.
[0069] The sulfiding agent can be any suitable sulfiding agent
known to be able to react with the solution of the copper salt to
form copper sulfide. The term sulfiding agent as used herein refers
to a compound that can react with the copper ions in the solution
by acting as a source of sulfur atoms or ions so as to form the
copper sulfide. The sulfiding agent may comprise alkali metal
sulfides or polysulfides, alkali earth metal sulfides or
polysulfides, ammonium sulfides or polysulfides, hydrogen sulfide
and disulfide, or mixtures thereof. Examples of sulfiding agents
include sodium sulfide, sodium disulfide, sodium polysulfide,
potassium sulfide, potassium disulfide and potassium polysulfide,
aluminium sulfide, magnesium sulfide, thiolacetic acid, thiobenzoic
acid, and mixtures thereof. Preferably, the sulfiding agent
comprises an alkali metal sulfide, ammonium sulfide, hydrogen
sulfide, or mixtures thereof. More preferably, the sulfiding agent
comprises sodium sulfide, ammonium sulfide, hydrogen sulfide, or
mixtures thereof. Most preferably, the sulfiding agent comprises
ammonium sulfide.
[0070] Preferably, the sulfiding agent is also in solution. When
the sulfiding agent is a soluble salt such as an alkali or alkali
earth metal salt (e.g. sodium sulfide) or ammonium sulfide, the
sulfiding agent is preferably in an aqueous solution. The sulfiding
agent is typically present in the aqueous solution in an amount of
from 8 to 50 weight percent, preferably from 25 to 50 weight
percent, and most preferably about 50 weight percent.
[0071] The aqueous solution of the copper salt and the aqueous
solution of the sulfiding agent comprise water. The water can be
from any suitable source such as tap water, deionised water, brine,
or any other suitable source of water. The solutions preferably
only comprise the copper (II) chloride or sulfiding agent and
water. However, solutions comprising other components may also be
used (for example minor amounts of other dissolved salts such as
sodium chloride).
[0072] When the sulfiding agent is a compound dissolved in aqueous
solution such as sodium sulfide or ammonium sulfide, step (i) of
reacting the aqueous solution of copper salt and aqueous solution
of sulfiding agent may comprise adding the solution of sulfiding
agent to a flask containing the copper salt solution. For example,
an aqueous solution of sulfiding agent can be added to a flask
containing the copper salt solution through a septum via a syringe
and needle. Optionally, the system is connected to a guard bed such
as a zinc oxide guard bed to trap any hydrogen sulfide and hydrogen
chloride released as by-products of the reaction. The use of such a
guard bed in such a system as described above is familiar to the
person skilled in the art.
[0073] Alternatively, the step of reacting the aqueous solution of
copper salt with the sulfiding agent may comprise adding the
solution of the copper salt into a solution of the sulfiding agent.
For example, the step may comprise adding a solution of a copper
halide such as copper (II) chloride to an aqueous solution of an
ammonium sulfide, alkali metal sulfide or alkali earth metal
halide. In an embodiment, the reacting step comprises adding an
aqueous solution of copper (II) chloride to an aqueous solution of
ammonium sulfide. As discussed in more detail below, copper sulfide
produced by the process has been found to have an enhanced mercury
removal ability. Surprisingly, and without being limited by theory,
it has been found that when a solution of the copper salt such as
copper (II) chloride is added to a solution of the sulfiding agent
such as ammonium sulfide, the time taken until mercury breakthrough
is longer (i.e. improved mercury removal ability) than when an
aqueous solution of the sulfiding agent (such as ammonium sulfide)
is added to the aqueous solution of the copper salt such as copper
(II) chloride. For example, when copper (II) chloride solution is
added into a flask containing ammonium sulfide, it has been found
that the mercury breakthrough time of the copper sulfide formed
from such a process is more than two times the mercury breakthrough
time of copper sulfide formed from a process where ammonium sulfide
is added into a flask containing copper (II) chloride. The sequence
of addition of the two reagents to one another has thus been found
to have an impact upon the properties of the copper sulfide formed
from such a process, such as the ability of the copper sulfide to
remove mercury from hydrocarbon fluid streams.
[0074] Thus, in a particularly advantageous instance, the process
of reacting the aqueous solution of copper salt with the sulfiding
agent comprises adding an aqueous solution of the copper salt such
as copper (II) chloride into a flask of the aqueous solution of the
sulfiding agent such as ammonium sulfide.
[0075] Preferably, step (i) of reacting the aqueous solution of
copper salt and aqueous solution of sulfiding agent comprises
stirring the reaction mixture for a time period of from 10 minutes
to 30 minutes.
[0076] During the mixture and reaction of the two solutions, copper
sulfide is precipitated from the solution as a black
precipitate.
[0077] After the reaction, the mixture is preferably left to stand
for a time period of from 5 minutes to 60 minutes.
[0078] When the sulfiding agent is a gas such as hydrogen sulfide,
the sulfiding agent is not reacted with the copper salt solution as
an aqueous solution but by a means suitable for reacting gases with
a compound dissolved in an aqueous solution. Such means are known
by the person skilled in the art. For example, hydrogen sulfide gas
in nitrogen can be bubbled through the copper salt solution for a
sufficient time for the hydrogen sulfide to react with the copper
ions in solution and yield the black copper sulfide precipitate.
For example, hydrogen sulfide gas in nitrogen can be bubbled
through the copper (II) chloride solution for a time period of from
25 to 65 hours, preferably 40 to 50 hours, and most preferably
about 45 hours. The concentration of the hydrogen sulfide in the
nitrogen can be, for example, 50 ppm to 250 ppm, preferably 75 ppm
to 125 ppm and most preferably about 100 ppm.
[0079] The sulfiding agent is reacted with the copper salt in a
molar excess. In the process, the copper salt used is contacted
with a greater amount of moles of sulfiding agent. Preferably, for
every one mole of the copper salt present, the copper salt is
contacted with from 1.1 to 1.5 moles of sulfiding agent, more
preferably from 1.05 to 1.2 moles of sulfiding agent, and most
preferably 1.1 moles of sulfiding agent.
[0080] The copper sulfide precipitate is then isolated from the
reaction mixture by any suitable means known in the art. Such
isolation means will be known to the person skilled in the art.
Suitably, the copper sulfide precipitate is isolated by filtration
with a suitably sized filter paper. In such a process, the reaction
mixture is poured onto a filter paper such that the water and
dissolved species pass through the filter paper whereas the copper
sulfide precipitate does not. In such a way, the copper sulfide
precipitate is isolated form the reaction mixture. Other species
dissolved in the solution may include soluble by-products of the
reaction and unreacted starting materials such as dissolved copper
(II) chloride, ammonium sulfide, sodium sulfide etc. A suitable
sized filter paper is one that the copper sulfide precipitate
particles cannot pass through.
[0081] After filtration, the copper sulfide precipitate is
preferably washed with deionised water to remove further impurities
from the precipitate. This entails pouring deionised water onto the
precipitate whilst it is on the filter paper such that the
deionised water passes over the precipitate and through the filter
paper dissolving any impurities as it goes and transporting them
through the filter paper.
[0082] The copper sulfide precipitate is then dried for a time
period of, typically, less than 48 hours, such as for a time period
of from 1 hour to 48 hours. The drying can be carried out in air or
in vacuum.
[0083] The drying is carried out at a temperature of less than
100.degree. C. The drying can be carried out at a temperature of
less than 90.degree., less than 80.degree. C., less than 70.degree.
C., less than 60.degree. C., less than 50.degree. C., less than
40.degree. C., or less than 30.degree. C.
[0084] Preferably, the drying is carried out a temperature of more
than 0.degree. C. Preferably, the drying is carried out a
temperature of less than 60.degree. C. Most preferably, the drying
is carried out a temperature of from 15.degree. C. to 50.degree.
C.
[0085] When the drying of the precipitate is carried out in air,
preferably, the drying is carried out at a temperature of less than
70.degree. C., less than 60.degree. C., less than 50.degree. C.,
less than 40.degree. C. or, or less than 30.degree. C.
[0086] Most preferably, when the drying is carried out in air, the
drying is carried out a temperature of less than 60.degree. C. or
less than 50.degree. C.
[0087] When the drying of the precipitate is carried out under
vacuum, preferably, the drying is carried out at a temperature of
less than 100.degree. C., less than 90.degree. C., less than
80.degree. C., less than 70.degree. C., less than 60.degree. C.,
less than 50.degree. C., less than 40.degree. C. or less than
30.degree. C.
[0088] Most preferably, when the drying is carried out under
vacuum, the drying is carried out at a temperature of less than
80.degree. C. or less than 70.degree. C.
[0089] Without being limited by theory, it is postulated that the
temperature of the drying step is useful to the process since the
novel form of copper sulfide of the invention has been found to
have enhanced mercury removal ability. This enhanced mercury
removal ability is reduced when the copper sulfide is dried above
certain temperatures. This is postulated to be because the novel
form of copper sulfide converts to a different form with decreased
mercury removal ability above certain temperatures. It is believed
that drying at a higher temperature under vacuum is possible whilst
retaining good mercury removal ability compared with drying in the
presence of air, since it is believed that the novel form of copper
sulfide may at least partially oxidise in the presence of air to a
form with decreased mercury removal ability.
[0090] It has been found that when copper sulfide of the invention
has an unexpected increased ability to remove mercury from a
mercury-containing fluid streams compared to existing forms of
copper sulfide. Copper sulfide prepared by the processes discussed
above has been found to have a previously uncharacterised
nanocrystalline form.
[0091] Surprisingly, the exact nature of the nanocrystalline form
has been found to vary depending upon the process used to
synthesise it. Where an ammonium sulfide sulfiding agent is used,
the nanocrystalline form of copper sulfide of the invention
generally comprises needle shaped nanocrystalline structures with a
length of generally from 100 nm to 200 nm, and a diameter of
generally from 10 to 20 nm. These are the nano-needle structures
discussed above.
[0092] On the other hand, where the sulfiding agent is sodium
sulfide or hydrogen sulfide, the nanocrystalline form of copper
sulfide of the invention generally comprises oval shaped
nanostructures, such as those discussed above.
[0093] Preferably, the copper sulfide according to the present
invention comprises or consists of nanocrystalline needle like
structures such as those discussed above. Preferably, the needle
like nanocrystalline structures are formed when the copper sulfide
according to the present invention is made via a process employing
an ammonium sulfide sulfiding agent.
[0094] The nanocrystalline forms of copper sulfide according to the
present invention have been found to have a higher mercury removal
ability than known forms of copper sulfide. Of the nanocrystalline
forms of copper sulfide according to the invention discussed above,
it has been found that the nanocrystalline needle structures of
copper sulfide that are typically prepared using an ammonium
sulfide sulfiding agent have a higher mercury removal ability than
the oval structure nanocrystalline forms of copper sulfide that are
typically prepared by the process using sodium sulfide and hydrogen
sulfide as the sulfiding agent. Nevertheless, the oval
nanostructures typically prepared from sodium sulfide and hydrogen
sulfide sulfiding agents still have an enhanced mercury removal
ability compared to forms of copper sulfide known in the art.
[0095] Without being limited by theory, it is postulated that the
enhanced mercury removal ability of copper sulfide of the invention
could be associated with the greater surface area of crystalline
nanoparticles compared to known forms of copper sulfide that may
have lower surface areas. This could be due to the higher surface
area material having a greater amount of active sites that mercury
can adsorb to thus removing it from a fluid stream. This theory
would explain why it has been found that the nano-needle structures
typically prepared with ammonium sulfide as the sulfiding agent
have enhanced mercury removal ability compared to the oval
nanostructures typically produced when sodium sulfide or hydrogen
sulfide are the sulfiding agent which have a lower surface
area.
[0096] As discussed above, it has been found that the temperature
of the drying step in the process of preparation is linked to the
enhanced removal of the copper sulfide to remove mercury from fluid
streams. This is postulated to be that above a certain temperature,
the nanostructures agglomerate decreasing the surface area of the
copper sulfide, decreasing the amount of active sites available for
mercury. Above yet a higher temperature, the nanostructures may
degrade into a different form of copper sulfide altogether such as
microcrystalline copper sulfide.
[0097] It has been found that where copper sulfide is prepared
according to a process using ammonium sulfide, sodium sulfide or
hydrogen sulfide, the ability of the copper sulfide to remove
mercury from a fluid feed decreases if the copper sulfide is dried
at higher temperatures. It has also been found that the mercury
removal ability of copper sulfide prepared according to the process
has best mercury removal ability when prepared using ammonium
sulfide, followed by sodium sulfide, followed by hydrogen
sulfide.
[0098] Thus, most preferably, the temperature used during drying is
low (such as below 60.degree. C. or 50.degree. C. in air, or below
80.degree. C. or 70.degree. C. in vacuum), and the sulfiding agent
comprises ammonium sulfide, sodium sulfide or hydrogen sulfide.
Most preferably, the sulfiding agent comprises ammonium
sulfide.
[0099] The processes described above can be done in the presence or
absence of a binder material or support material. In the
manufacture of many sorbents, the active material (i.e. copper
sulfide or other material that acts to absorb/adsorb) is often
synthesised with binder or support material in the reaction mixture
so as to produce sorbent particles that comprise a binder or
support material with an adsorbent/absorbent material upon its
surface. Examples of such support materials and binder materials
commonly used include activated carbon, silicates, alumina,
titanium, zirconia, alumina-silicate, metal aluminate, hydrated
metal oxide, mixed metal oxide, metal carbonates, cement, zeolite,
a ceramic material, clay, cement, polymers, or any combination
thereof. It is preferred that the processes described above are
carried out in the absence of any binders or support materials such
as those discussed above present in the reaction mixture. However,
in the alternative, the processes described above may be carried
out in the presence of one or more binders or support materials,
such as those discussed above.
[0100] Sorbents of the present invention may comprise the copper
sulfide of the invention and optionally one or more binder or
support materials, such as those discussed above. Where the
sorbents of the invention comprise one or more binder or one or
more support materials, the copper sulfide of the invention may be
synthesised initially before the dried copper sulfide is mixed with
the support or binder to form a sorbent. In this scenario, it will
be appreciated that the support or binder is not present when the
processes described above are carried out to produce the copper
sulfide. As such, the one or more binders or support materials are
not included in the reaction mixture of the processes and the
copper sulfide is dried in the absence of the binder or support
material before being applied to or mixed with the one or more
binders or support materials in a dry form to form a sorbent of the
present invention.
[0101] The copper sulfide of the present invention has been found
to reduce the mercury content of fluid streams flowing past the
copper sulfide. Because of this, it is postulated that the copper
sulfide of the invention could find utility in a wide variety of
industrial applications as the active component of a sorbent. It is
believed that the copper sulfide of the invention could find
utility in removing environmental pollutants such as heavy metals
from liquid or gaseous fluid streams. The term "heavy metals" as
used herein typically refers to metals which may cause damage to
the environment or human health when exposure occurs at high enough
doses. Typically, the term "heavy metals" encompasses chromium,
arsenic, cadmium, mercury and lead. However, the term may
additionally be used to refer to manganese, cobalt, nickel, copper,
zinc, selenium, silver, tin, antimony and thallium. Preferably, the
copper sulfide of the present invention is used to remove mercury
from fluid streams.
[0102] Use according to the present invention comprises using the
copper sulfide of the invention to remove heavy metals such as
mercury from fluid streams such as liquid or gaseous fluid streams.
The fluid streams may comprise water streams, flue gas streams,
industrial process streams such as industrial gas process streams,
or hydrocarbon streams such as crude oil, wet natural gas and dry
natural gas. In such uses, the copper sulfide acts as a sorbent.
The sorbent comprising copper sulfide particles of the invention
can comprise one or more support materials or one or more binder
materials such as those discussed above. Alternatively, when used
as a sorbent, the copper sulfide of the present invention may be
unsupported and not be in the presence of one or more binder
materials or one or more support materials.
[0103] Thus, according to a further aspect of the invention, there
is provided a process for the removal of mercury from a
mercury-containing hydrocarbon fluid stream comprising the steps
of: [0104] (i) contacting the mercury-containing hydrocarbon fluid
stream with a sorbent comprising copper sulfide of the formula
Cu.sub.xS.sub.y, wherein x and y are integer or non-integer values;
and [0105] (ii) separating a fluid product from the sorbent,
wherein the fluid product has a reduced mercury content compared to
the mercury-containing hydrocarbon fluid stream; wherein the copper
sulfide is according to any of the above described aspects of the
invention.
[0106] Preferably, the copper sulfide is obtained or obtainable by
the process steps discussed above.
[0107] Mercury-containing hydrocarbon fluids that can be processed
according to the present invention may typically comprise from 1
part per billion (ppb) of mercury to 2000 parts per million (ppm)
of mercury. For example, hydrocarbons fluids that can be processed
can comprise 2 to 10,000 ppb of mercury; or 5 to 1000 ppb of
mercury. The mercury content of naturally occurring hydrocarbon
fluids may take a variety of forms, and the present invention can
be applied to the removal of elemental mercury, particulate
mercury, organic mercury or ionic mercury from hydrocarbon fluids.
In one preferred embodiment, the mercury is in one or more of
elemental, particulate or organic form. Still more preferably, the
mercury is in elemental form.
[0108] The process of the invention may be applied to substantially
any hydrocarbon fluid stream which comprises mercury, and which is
liquid or gaseous under the operating conditions of the process.
Thus, hydrocarbon fluid streams that may be processed according to
the present invention include liquid hydrocarbons, such as
liquefied natural gas; light distillates, e.g. comprising liquid
petroleum gas, gasoline, and/or naphtha; natural gas condensates;
middle distillates, e.g. comprising kerosene and/or diesel; heavy
distillates, e.g. fuel oil; and crude oils. Hydrocarbon fluids that
may be processed according to the present invention also include
gaseous hydrocarbons, such as natural gas and refinery gas.
Preferably the hydrocarbon fluid comprises natural gas, and most
preferably, wet natural gas.
[0109] Generally, it is most economical to contact the copper
sulfide sorbent and the mercury-containing hydrocarbon fluid feed
without the application of heat, and refinery product streams may
be conveniently treated at the temperature at which they emerge
from the refinery, which is typically in the range of from
-80.degree. C. to 200.degree. C. The copper sulfide sorbent and
mercury-containing fluid feed can be contacted at any suitable
pressure for the reaction to take place between the copper sulfide
and the mercury in the hydrocarbon fluid stream, for example,
atmospheric pressure.
[0110] In accordance with the process of the present invention, the
copper sulfide sorbent extracts at least 60 wt % of the mercury
content of the mercury-containing hydrocarbon fluid stream. More
preferably, the copper sulfide sorbent extracts at least 70 wt %,
still more preferably at least 80 wt %, still more preferably at
least 90 wt %, still more preferably at least 95 wt %, and most
preferably greater than 99 wt % of the mercury content of the
mercury-containing hydrocarbon fluid stream.
[0111] Thus, in accordance with the process of the present
invention, a hydrocarbon fluid product may be obtained which
comprises 10% or less of the mercury content of the
mercury-containing hydrocarbon fluid stream. More preferably the
hydrocarbon fluid product comprises 5% or less of the mercury
content of the mercury-containing hydrocarbon fluid stream, and
most preferably the hydrocarbon fluid product comprises 1% or less
of the mercury content of the mercury-containing hydrocarbon fluid
stream.
[0112] Preferably the mercury concentration of the hydrocarbon
fluid product of the process of the invention is less than 50 ppb,
more preferably less than 10 ppb, and most preferably less than 5
ppb.
[0113] The copper sulfide sorbent and the mercury-containing
hydrocarbon fluid stream may be contacted by either continuous
processes or batch processes. Any conventional solid-liquid or
solid-gas contactor apparatus may be used in accordance with the
present invention.
[0114] The process of the invention may be repeated on the same
mercury-containing hydrocarbon fluid feed in a series of contacting
steps, e.g. two to ten, to obtain a successive reduction in the
mercury content of the hydrocarbon fluid product at each step.
[0115] The copper sulfide sorbent is allowed to contact the
mercury-containing hydrocarbon fluid stream for sufficient time to
enable at least a portion of the mercury in the mercury-containing
hydrocarbon fluid stream to adsorb or absorb to the sorbent
comprising copper sulfide. Suitable timescales include from 1
second to 5 hours.
[0116] The copper sulfide sorbent according to the present
invention, or used in the process of the present invention may be
supported on one or more support materials, or may be in the
presence of one or more binder materials, or may be in the presence
of both one or more support materials and one or more binder
materials. Alternatively, the copper sulfide sorbent used in the
process of the present invention may be free of one or more support
materials or one or more binder materials. The one or more binder
materials or one or more support materials that the copper sulfide
sorbent may comprise or be free of may be inert materials. The one
or more binder materials or one or more support materials that the
copper sulfide sorbent may comprise or be free of may comprise
silicates, alumina, titanium, zirconia, alumina-silicate, metal
aluminate, hydrated metal oxide, mixed metal oxide, metal
carbonates, cement, zeolite, a ceramic material, clay, cement,
polymers, or any combination thereof.
[0117] Accordingly, the copper sulfide sorbent according to the
present invention, or used in the process of the present invention
may contain only copper sulfide of the present invention, and be
free of one or more binder materials and/or one or more support
materials such as the materials discussed above.
[0118] The process of the present invention may be used in
combination with other known methods for the removal of mercury
from hydrocarbon fluids. However, the process of the invention may
alternatively be sufficient to remove mercury from hydrocarbon
fluid streams to a sufficient extent such that it is not necessary
to use any other processes for mercury removal in combination.
[0119] According to another aspect of the invention, there is
provided a mercury removal sorbent comprising copper sulfide
obtained or obtainable by the process of the invention discussed
above. The mercury removal sorbent comprising copper sulfide may
comprise or may not comprise any of the features discussed above
for the copper sulfide sorbent discussed above in the context of
the process of the invention for removing mercury from
mercury-containing hydrocarbon fluid streams. According to another
aspect of the invention, there is provided a mercury removal
sorbent comprising copper sulfide obtained or obtainable by the
processes discussed above. The mercury removal sorbent comprising
copper sulfide may comprise or may not comprise any of the features
discussed above for the copper sulfide sorbent discussed above in
the context of the process of the invention for removing mercury
from mercury-containing hydrocarbon fluid streams.
EXAMPLE
[0120] The following examples are not to be considered as limiting
the scope of the claims and are included merely to exemplify
certain embodiments of the process of the present invention.
Step-by-Step Preparation of 5 g of the Cu.sub.xS.sub.y Material
Using (NH.sub.4).sub.2S as Sulfide Source
[0121] Copper sulfide according to the invention was prepared by
the following process:
[0122] Preparation of 5 g of copper sulfide requires 7.034 g
CuCl.sub.2 anhydrous & 7.823 g of (NH.sub.4).sub.2S (mol ratio
1:1.1 respectively) using an excess of (NH.sub.4).sub.2S.
[0123] 1. Weigh 7.034 g of CuCl.sub.2 anhydrous in 100 ml two
necked round bottomed flask and make 1 M CuCl.sub.2 solution in
H.sub.2O by adding 52.3 ml of water into the flask.
[0124] 2. Stir the solution until all CuCl.sub.2 dissolved in
H.sub.2O and a clear light blue solution is provided.
[0125] 3. A previously weighed (NH.sub.4).sub.2S 50 wt % solution
in H.sub.2O was added through a septum using a syringe and needle
until all 7.823 g of (NH.sub.4).sub.2S in H.sub.2O was added
completely while stirring maintained (through the other neck of the
flask). The system was connected to a zinc-oxide guard-bed to trap
any H.sub.2S released and the outlet released into a beaker of
water to remove the hydrogen chloride.
[0126] 4. The mixture in the flask was continuously stirred for 15
minutes using a stirrer bar (rigorous stirring is not needed since
the reaction kinetics are fast). A black copper sulfide precipitate
is then obtained in the solution.
[0127] 5. The sample is left for ageing for not more than an
hour.
[0128] 6. The solution was filtered using filter paper (5-13
.quadrature.m size) and the filtered solids were then washed using
de-ionised water until the filtrate solution turned from pale
yellow to colourless (.about.1 g product washed using 100 ml
H.sub.2O). Washing removes excess (NH.sub.4).sub.2S, CuCl.sub.2 and
any soluble by-products.
[0129] 7. Filtered solid dried in air for no longer than 2
days.
[0130] Cu.sub.xS.sub.y materials were also prepared using various
sulfiding sources such as Na.sub.2S and H.sub.2S. In the case of
Na.sub.2S, the preparation procedure was followed the same as for
(NH.sub.4).sub.2S discussed above. When H.sub.2S was the sulfiding
source, 100 ppm H.sub.2S gas in nitrogen was bubbled through 1 M
CuCl.sub.2 aqueous solution for 45 h resulting in 0.53 g of
Cu.sub.xS.sub.y material.
[0131] Mercury Extraction Studies
[0132] All mercury extraction experiments were carried out using
nitrogen as carrier gas using the set-up shown in FIG. 9 (a) dry
gas testing and (b) wet-gas testing. How to configure and use the
apparatus for testing mercury extraction performance will be
apparent to those of skill in the art.
[0133] Based on the preparation methodology explained in the
example above, the Cu.sub.xS.sub.y samples synthesized are listed
below:
[0134] 1. Cu.sub.xS.sub.y ((NH.sub.4).sub.2S+CuCl.sub.2) air
ambient drying--SI-NH
[0135] 2. Cu.sub.xS.sub.y ((NH.sub.4).sub.2S+CuCl.sub.2) air
90.degree. C. drying--SII-NH
[0136] 3. Cu.sub.xS.sub.y ((NH.sub.4).sub.2S+CuCl.sub.2) vacuum
90.degree. C. drying--SIII-NH
[0137] 4. Cu.sub.xS.sub.y ((NH.sub.4).sub.2S+CuCl.sub.2) air
90.degree. C., vacuum 250.degree. C. drying--SIV-NH
[0138] 5. Cu.sub.xS.sub.y ((NH.sub.4).sub.2S+CuCl.sub.2) vacuum
90.degree. C., vacuum 250.degree. C. drying--SV-NH
[0139] 6. Cu.sub.xS.sub.y (Na.sub.2S+CuCl.sub.2) air ambient
drying--SI-Na
[0140] 7. Cu.sub.xS.sub.y (Na.sub.2S+CuCl.sub.2) air 90.degree. C.
drying--SII-Na
[0141] 8. Cu.sub.xS.sub.y (Na.sub.2S+CuCl.sub.2) air 90.degree. C.,
vacuum 250.degree. C. drying--SIV-Na
[0142] 9. Cu.sub.xS.sub.y (H.sub.2S+CuCl.sub.2) air ambient
drying--SI-H
[0143] 10. Cu.sub.xS.sub.y (H.sub.2S+CuCl.sub.2) air 90.degree. C.
drying--SII-H
[0144] 11. Cu.sub.xS.sub.y (H.sub.2S+CuCl.sub.2) air 90.degree. C.,
vacuum 250.degree. C. drying--SIV-H
[0145] "Ambient temperature" as described above is 20.degree.
C.
[0146] The breakthrough test was conducted with a flow rate of 600
ml/min, 2000 ng/L Hg & 0.03 g of sample weight using Sir
Galahad II mercury analyser. Mercury removal performance for SI-NH
(air dried in ambient) possesses good extraction performance
without indication of mercury breakthrough after more than 60
hours. The results are shown in FIG. 1.
[0147] This result is compared with various treated Cu.sub.xS.sub.y
materials SII-NH and SIV-NH as shown in FIG. 2. Since the
breakthrough hours were very long, the testing conditions were
modified to achieve mercury breakthrough and thereby also reproduce
the extraction performance of SI-NH; sample size was reduced as
0.01 g to accelerate the breakthrough process. Cu.sub.xS.sub.y
materials were also prepared using various sulfiding sources. The
mercury breakthrough plots for the Cu.sub.xS.sub.y samples prepared
from (NH.sub.4).sub.2S, Na.sub.2S and H.sub.2S as sulfiding
sources, are shown in FIGS. 2-5.
[0148] FIG. 2 shows the mercury extraction performance results for
the sample dried in air at ambient (SI-NH) followed by drying the
same sample in air at 90.degree. C. (SII-NH) and further heating at
250.degree. C. in vacuum (SIV-NH). FIG. 3 shows the results for
SI-NH, SIII-NH samples that are dried in vacuum at 90.degree. C.
and further heated at 250.degree. C. that produced SV-NH. Comparing
the results from FIGS. 2 and 3, SI-NH clearly outperforms other
samples with breakthrough time of 13 hours which is consistent with
the findings when tested at standard testing conditions using 0.03
g of sample in the fixed bed reactor (FIG. 9).
[0149] FIG. 4 shows the mercury removal performance for samples
SI-Na, SII-Na and SIV-Na that was conducted using 0.01 g sample
loaded in the fixed bed reactor in order to further accelerate the
breakthrough as discussed earlier. SI-Na sample (sample dried in
ambient air) showed the highest performance amongst for SI-Na,
SII-Na & SIV-Na with breakthrough time around 9 hours but this
is still lower than the SI-NH sample that possessed 13 hours of
breakthrough time.
[0150] Heating the sample in air at 90.degree. C. significantly
reduced the performance to 0.3 hours but further heating in vacuum
at 250.degree. C. has increased the performance slightly to 0.5
hours. The trend for mercury removal performance is the same as the
sample prepared from (NH.sub.4).sub.2S but the magnitude is
different since the sample prepared from (NH.sub.4).sub.2S has
better performance. Sample drying in ambient air enhances the
extraction performance in both cases.
[0151] FIG. 5 shows the mercury removal performance for the SI-H,
SII-H and SIV-H that was conducted using 0.01 g sample in the fixed
bed reactor. SI-H sample which is the sample dried in ambient air
showed the highest performance with around 7 hours breakthrough but
this is lower from the SI-NH and SI-Na sample that provided 13 and
9 hours of elemental mercury extraction performance respectively.
Heating the sample in air at 90.degree. C. has reduced the
performance to 2.7 hours and further heating in vacuum at
250.degree. C. reduced the extraction performance to 1 hour. The
trend for mercury removal performance is different from the sample
prepared from (NH.sub.4).sub.2S and Na.sub.2S where for the case of
sample from (NH.sub.4).sub.2S and Na.sub.2S heating in air at
90.degree. C. reduced the performance significantly but further
heating in vacuum at 250.degree. C. has retrieved the performance
to certain extent.
[0152] As a summary, FIG. 6 shows mercury removal performance of
the Cu.sub.xS.sub.y-(NH.sub.4).sub.2S samples using different
drying techniques and FIG. 7 shows the performance of the air
ambient drying samples for copper sulfide prepared using the
sulfiding agents (NH.sub.4).sub.2S, Na.sub.2S and H.sub.2S.
[0153] Transmission Electron Microscopy (TEM) Studies
[0154] The following samples were analysed by Transmission Electron
Microscopy (TEM):
[0155] SI-NH (ammonium sulfide as sulfiding agent and air dried
under ambient conditions);
[0156] SIII-NH (ammonium sulfide as sulfiding agent and vacuum
dried at 90.degree. C.);
[0157] Copper sulfide purchased from Sigma Aldrich;
[0158] SI-Na (sodium sulfide as sulfiding agent and air dried under
ambient conditions);
[0159] SI-H (hydrogen sulfide as sulfiding agent and air dried
under ambient conditions).
[0160] From FIG. 10--Error! Reference source not found.2, the
difference can clearly be seen between the TEM images obtained for
each of the samples. SI-NH (as shown in FIG. 10) can be seen to
show a fine distribution of nano-crystalline particles (i.e.
nano-needles) with the length of .about.20-150 nm and diameter of
.about.10-20 nm. For SIII-NH sample which was dried at elevated
temperature, 90.degree. C. in vacuum (see FIG. 11), it can be seen
that nano-crystalline particles have started to agglomerate, which
might cause reduction in active sites. This can be correlated to
the mercury removal performance of both samples, SI-NH vs SIII-NH,
where SI-NH was tested to have a much better performance for
mercury removal in comparison to SIII-NH, 13.5 vs 2 h.
[0161] Furthermore, TEM images for CuS-Sigma-Aldrich as can be seen
in Error! Reference source not found.2, showed that it is opaque
due to bigger size particles. Therefore, it can be said that the
heat treatment has transformed the sample from nano-crystalline
particles that start to agglomerate on heating and become bigger
sized, which is thought to have a direct impact on the mercury
removal performance.
[0162] It has been shown that drying temperature affects the
crystalline nature of the sample (i.e. nano-crystal transformed
into macro or bigger crystal as temperature treatment increases),
and how this has impacted the mercury removal performance. It would
also be appropriate to compare the TEM analysis of samples that
were produced using different sulfide sources (i.e. SI-NH, SI-NA
and SI-H), and the TEM images can be seen in FIG. 13.
[0163] From FIG. 13, it can be seen that the agglomeration of
particles increases, moving from SI-NH to SI-Na and finally to
SI-H. For SI-Na, variable shapes of nano-crystalline particles were
formed, and in the case of SI-H no specific shaped
nano-crystallites were formed. These observations were also in line
with the mercury removal performance, where mercury removal
performance for SI-NH>SI-Na>SI-H. It can be said that
temperature and sulfide sources influenced the formation of
nano-crystallites that leads to well dispersed solid particles, and
may account for the enhanced mercury extraction performance, with
the best mercury removal performance being SI-NH.
[0164] FIG. 14 shows the difference in mercury breakthrough time
between various copper sulfides produced according to different
process described above. The graph compares mercury breakthrough
for copper sulfide produced from a process where copper chloride
solution is added to a flask containing ammonium sulfide solution
with copper sulfide produced from a process where the ammonium
sulfide solution is added to a flask containing copper chloride
solution. The graph also shows mercury breakthrough for copper
sulfide obtained via a process of the invention where a copper
chloride solution is simultaneously added to an ammonium sulfide
solution. It can be seen that when a solution of copper chloride is
added to a flask containing a solution of ammonium sulfide, the
resultant copper sulfide has an enhanced mercury removal ability
than vice versa and an enhanced mercury removal ability than
simultaneous addition of the solutions.
[0165] It should be noted that whilst particle size of the copper
sulfide is thought to increase the mercury removal performance of
the copper sulfide, it is believed that this is not the sole reason
for the enhanced mercury removal ability. Other factors are found
to influence the mercury removal ability such as sulfiding agent,
copper salt and sequence of addition of the reagents. Without being
limited by theory, it is postulated that factors such as the
oxidation states of the copper and sulfide ions in the new form of
copper sulfide according to the invention may impact the mercury
removal performance.
X-Ray Photoelectron Spectroscopy Studies (XPS)
[0166] XPS spectra of the SI-NH sample discussed above were
obtained and contrasted with XPS spectra of copper sulfide
purchased from Sigma Aldrich. Spectra were obtained using a Kratos
AXIS Ultra DLD apparatus, equipped with a monochromatic Al-K.alpha.
X-ray source, a charge neutraliser and a hemispherical electron
energy analyser. The chamber pressure was kept below 10.sup.-9 mbar
during data acquisition. The spectra were analysed using the
CasaXPS software package and corrected for charging using C 1s
binding energy (BE) as the reference at 284.8 eV.
[0167] FIG. 15 is the copper 2p XPS spectrum of SI-NH. FIG. 16 is
the sulfur 2p spectrum for SI-NH. FIG. 17 is the copper 2p XPS
spectrum of copper sulfide purchased from Sigma Aldrich. FIG. 18 is
the sulfur 2p XPS spectrum of copper sulfide purchased from Sigma
Aldrich. Comparing FIGS. 15 and 17, it can be seen that the copper
sulfide of the present invention has a distinct copper 2p XPS
spectrum from copper sulfide purchased form Sigma Aldrich. The
SI-NH copper sulfide copper 2p spectrum does not comprise any
satellite peaks which indicates that the copper is predominantly in
the copper (I) oxidation state. On the other hand, the copper 2p
spectrum of copper sulfide purchased from Sigma Aldrich contains
identifiable satellite peaks at 939.8 eV (.+-.3eV) and 943.1 eV
(.+-.3 eV) which indicate that copper in both the copper (I) and
copper (II) oxidation state is present. Comparing FIGS. 16 and 18,
it can be seen that for the sulfur 2p spectrum of SI-NH, there are
peaks at 162.3 eV (.+-.1 ev), 163.8 eV (.+-.1 ev) and 168.5 eV
(.+-.1 ev), and that the peak at 168.5 eV has a lower value of
counts per second (CPS) than both the peak at 162.3 eV and the peak
at 163.8 eV. In contrast, from FIG. 18, it can be seen that for the
sulfur 2p spectrum of copper sulfide purchased from Sigma Aldrich,
the peak at 168.5 eV has a higher value of counts than the other
two peaks.
[0168] The XPS data thus shows that copper sulfide according to the
present invention has distinct XPS spectra from copper sulfide
known in the art such as that purchased from Sigma Aldrich. The
copper sulfide of the present invention is thus shown to be a novel
form of the compound with XPS spectra distinct from spectra of
forms of copper sulfide known in the art.
[0169] X-Ray Powder Diffraction Studies (XRPD)
[0170] X-ray powder diffraction spectra were obtained using a
PANalytical X'Pert PRO powder diffractometer equipped with
Cu-K.alpha. X-rays (X=1.5418 .ANG.) source. X-rays were generated
from a copper anode supplied with 40 kV and a current of 40 mA.
Data was recorded between 20 values of between 5.degree. and
90.degree., in steps of 0.017.degree., with a time period per step
of 5s.
[0171] Spectra were obtained for samples SI-NH, SII-NH, SIII-NH,
SV-NH, SI-Na, SI-H discussed above, and copper sulfide purchased
from Sigma Aldrich. The spectra for these samples are shown in the
following figures.
[0172] SI-NH--FIG. 19
[0173] SI-NH, SIII-NH, SV-NH, and copper sulfide purchased from
Sigma Aldrich--FIG. 20
[0174] SII-NH--FIG. 21
[0175] SI-Na--FIG. 22
[0176] SI-H--FIG. 23
[0177] Comparison of the spectrum of the SI-NH sample shown in FIG.
20 with that of the spectrum of copper sulfide purchase from Sigma
Aldrich show that the spectrum of copper sulfide of the invention
contains fewer peaks and broader peaks that the spectrum for copper
sulfide purchased from Sigma Aldrich. The peaks are also at
different values with different relative intensities. For the SI-NH
spectrum, the peak at 2.theta.=32.21 is the only peak in the
spectrum between the peak at 2.theta.=29.54 and 2.theta.=48.21. On
the other hand, the spectrum of copper sulfide obtained from Sigma
Aldrich can be seen to contain one or more peaks within this
range.
[0178] The broader peaks in the spectrum of SI-NH indicate that the
crystallite size of the copper sulfide is smaller and
nanocrystalline. On the other hand, the sharper, narrower peaks in
the spectrum of the copper sulfide purchased from Sigma Aldrich
indicate that the crystallite size of the copper sulfide is larger
and micro-crystalline.
[0179] Comparison of the spectrum of SI-NH with that of SI-Na and
SI-H show that the new form of copper sulfide of the invention may
be produced with a variety of different sulfiding agents (ammonium
sulfide, sodium sulfide and hydrogen sulfide).
[0180] Comparison of the SI-NH and SIII-H spectra show that when
the copper sulfide is dried at 90.degree. C. in vacuum, the
spectrum is largely unchanged indicating that the new
nanocrystalline form of the copper sulfide is still present and the
structure unchanged after drying at 90.degree. C. However,
comparison of the SIII-NH and SV-NH samples show that if the copper
sulfide is dried at 250.degree. C., the spectrum contains more
peaks which are sharper and narrower. This indicates that after
drying at higher temperatures the novel nanocrystalline form of
copper sulfide has changed into a microcrystalline form. The
spectrum of SV-NH more closely resembles the spectrum of the
microcrystalline copper sulfide purchased from Sigma Aldrich.
[0181] The spectrum of SII-NH shown in FIG. 21 compares the
spectrum of SI-NH further dried in air at 90.degree. C. with the
spectrum of copper sulphate. It can be seen that various peaks of
the copper sulphate appear in the spectrum of SII-NH and that the
SII-NH spectrum is remarkably different to that of SI-NH. This is
believed to be because the novel nanocrystalline form of copper
sulfide oxidises in air when dried at 90.degree. C. to form copper
sulphate. Thus, it is shown that drying in air at 90.degree. C.
degrades the copper sulfide of the invention.
* * * * *